1. Field of the Invention
The present invention relates to lasers. More specifically, the present invention relates to high energy lasers.
2. Description of the Related Art
High energy lasers are currently being evaluated for a variety of military and industrial applications. The implementation of a high energy weapon-class laser system is currently limited to large platforms only due to the relatively low power per weight ratio numbers in the present approaches.
Prior approaches for weapons class lasers include chemical and gas lasers, which have already demonstrated weapon level power. Other diode-pumped solid-state bulk and fiber-based approaches also have been proposed. The conventional chemical laser is a large and highly complex system. In addition, the chemical handling requirement makes this an extremely cumbersome and undesirable approach. The relatively clean diode-pumped solid-state laser approach is much more desirable.
However, diode-pumped solid-state lasers using bulk active media have problems such as high beam distortion as the beam propagates through the amplifier chain. Compensation for this distortion currently requires active (deformable mirror) or passive (such as non-linear phase conjugation) techniques. In addition, the gain elements for bulk diode-pumped solid-state lasers are currently comprised of complex, expensive composite slabs, which are prone to damage. In addition, the master oscillator—power amplifier (MOPA) approach, which is typically used to improve the beam quality of bulk solid-state lasers, limits the ultimate optical (and, therefore, the overall) conversion efficiency, which results in increased power and waste heat extraction real-estate requirements.
Fiber lasers have inherently high efficiencies because they operate at very high laser beam intensities and allow for 100% pump power absorption and can be cooled efficiently due to their inherently high surface to volume ratio relative to traditional bulk solid-state lasers. Fiber lasers, however, are limited with respect to the maximum power that they can operate at due to intensity damage threshold limits. Fiber lasers, therefore, typically require coherent phasing of multiple fiber oscillators to achieve high power levels. This adds a number of problems and associated complexities. Principal of which is alignment, sensitivity to vibration, and lack of a reliable and robust approach for coherent combining of multiple individual laser beams. Another problem is the requirement of complex beam combining/shaping optics to form one compact output beam out of an array of multiple individual beams. Production of a high quality output beam then requires scaling, dissipation of heat and some approach for dealing with the high concentration of energy in a small volume. This leads to increased system complexity and associated high costs.
Hence, a need exists in the art for a relatively unsophisticated system or method for substantially increasing the output power, efficiency, and beam quality of high-energy lasers.